For purposes of this specification, the term central air handling and conditioning apparatus refers to any system, such as a forced-air furnace or heater, air-conditioner, evaporative air cooler, fan or blower and the like or any combination thereof for circulating air in a plurality of enclosed spaces, such as different rooms in a building, and regulating the temperature of the air. The term dehumidifier refers to any apparatus for reducing the relative humidity of the air in an enclosed space by removing water vapor from the air and returning the dehumidified air to the enclosed space. Conditioned air is air which has been heated or cooled by a central air handling and conditioning apparatus. Dehumidified air is air which has been dehumidified by a dehumidifier. It has not previously been known to provide a central air handling and conditioning apparatus with a by-pass dehumidifier.
The temperature of the air in a plurality of enclosed spaces is often maintained within a predetermined range to provide comfort to the occupants. Regulating the temperature of the air alone, however, is not always sufficient to provide the desired degree of comfort. For example, although the temperature is within the desired range, the relative humidity may remain uncomfortably high. Typically, this situation occurs at higher elevations or near large bodies of water when the temperature at which water vapor begins to condense, or the dew point, is lower than the desired temperature. Thus, dehumidification by cooling is possible only by lowering the temperature of the conditioned air below the comfortable range.
As an alternative to additional cooling, a dehumidifier may be used to maintain the relative humidity of the air below a predetermined value. Separate air handling and conditioning apparatus and dehumidifiers are well known. It is also known to provide a single system which cools and dehumidifies, and which dehumidifies without cooling. Such a system is disclosed in U.S. Pat. No. 5,088,295 issued Feb. 18, 1992 to Shapiro-Baruch.
The patent to Shapiro-Baruch discloses an air conditioner with a dehumidification mode. The air conditioner operates on the conventional vapor compression principle, but includes a second inside heat exchanger and means for by-passing a portion of the flow of hot refrigerant through the second heat exchanger in the dehumidifying mode. A first inside heat exchanger acts as an evaporator to cool and dehumidify the air. The second heat exchanger is positioned in parallel with the first heat exchanger and acts as a heater to heat the air. By mixing the cooled and dehumidified air with the heated air, the conditioned air is dehumidified with little change in temperature. The Shapiro-Baruch air conditioner is particularly suited for room air conditioner applications. Thus, it is not readily adaptable to an existing central air handling and conditioning apparatus.
U.S. Pat. No. 2,255,292 issued Sep. 9, 1941, to Lincoln discloses a central air handling and conditioning apparatus. The Lincoln apparatus regulates the temperature and the relative humidity of the air within a plurality of rooms designed for human occupancy. A heat interchanger regulates the temperature of a fluid which is circulated through a radiator in each room. A fan or blower causes a flow of air to contact the radiator and thereby heat or cool the room. When the room is cooled in hot weather, an evaporator pan and drain collect the condensate which drips from the radiator into a central collector. The apparatus, however, does not include a by-pass dehumidifier. Thus, the Lincoln air handling and conditioning apparatus cannot dehumidify the air without further cooling the conditioned air.